The team has been testing exhaust emissions in a facility in Nidau for three years. The work has involved the collaboration of four organisations. According to a report by Swiss broadcaster SFR, researchers already knew that modern petrol engines were more polluting than diesels, but were surprised by the size of the difference. Modern fuel injection systems are to blame. While being more fuel efficient, they emit a lot more pollution.

Rainer Klose, one of the researchers, told SFR that their tests revealed that petrol cars produced 10 to 100 times more particulates than comparable diesel ones. He described the results as rather alarming given the carcinogenic substances contained in these soot particles.

Part of the problem is the small size of the particulates. Because they are so small once inhaled they stay in the lungs.

From October, new EU guidelines will require some modern petrol cars to be fitted with particulate filters, something that has been required on diesels for some time. Many petrol cars will escape the new requirements, something the researchers think is a mistake.

Switzerland’s Federal Office for the Environment is pleased with the results but thinks it will be decades before filters are fitted on all petrol cars. In an interview with SFR, Giovanni D’Urbano, departmental director for transport, alludes to the time required to get international parties to agree on new standards.